What is the difference between a reversible reactions which occurs in a closed system and an open system?

An Open System is one in which one or more of the reactants or products are able to escape from the container. A Closed  System is one in which neither the reactants or the products can escape from the container.

Cruicially, reversible reactions which occur in a closed system will eventually reach equilibrium. That is, the concentration of each reactant and product will not change and the forward and reverse reaction will continue at the same rate.